Graphene–ionic liquid electrolytes for dye sensitised solar cells

Abstract

In this work two dimensional graphene flakes were used to prepare new electrolytes for dye sensitized solar cells (DSSCs). Small amounts (up to 3 wt%) of graphene nanoflakes were suspended into the ionic liquid (IL) 1-propyl-3-methyl imidazolium iodide (PMII) to produce new electrolytes. The use of these electrolytes in DSSCs resulted in more than twenty five times improvement of the solar cell efficiency. The increase in efficiency can be attributed to two primary reasons. Graphene can act as an efficient charge transfer agent in the viscous IL and also as a catalyst for the electrochemical reduction of I₃⁻ in the electrolyte layer. In addition interactions between the graphene and the IL system lead to the formation of self-organised assemblies or networks. These factors not only provide an efficient electron transfer network through the electrolyte but also allow for the formation of quasi-solid electrolytes, at higher graphene concentrations. These electrolytes may find applications in advanced DSSC architectures, where a quasi-solid based system could eliminate problems associated with electrolyte leakage and solvent related degradation of materials.